Posted
by
kdawsonon Tuesday June 02, 2009 @02:39PM
from the sit-up-straight dept.

An anonymous reader sends along a piece in Cosmos about new dissension to the current prevailing wisdom on dinosaur posture. The researchers admit that blood pressure presents an unresolved obstacle to their model of dinosaur heads held high. "The current depiction of the way giant sauropod dinosaurs held their necks is probably wrong, says a new study. 'For the last decade the reigning paradigm in palaeontology has been that the big sauropod dinosaurs held their necks out straight and their heads down low,' said co-author Matt Wedel, who researches biomechanics at the Western University of Health Sciences in Pomona, California. But 'our research [now] suggests that this view of sauropods is simply incorrect, based on everything we know about living animals,' he said." The researchers worried that some other team might beat them to publication, so obvious did they consider their methodology of looking at living animals to gain insight into the biomechanics of extinct ones.

Why are we arguing over which position was the default when it's entirely possible that they utilized both positions. Down low for traveling to avoid blood pressure problems and up high for brief states of alert or reaching high food sources? With the flexibility of the vertebrae, I would assume the animal would use it however it most suited them for the time being.

The other thing is how much do we know about the tissues and proteins that made up muscles and blood in Sauropods? Is it possible that they were much stronger or their blood had different properties making it capable of overcoming the blood pressure problem?

I've seen exhibits that portray them both ways [wikipedia.org]. You just might have to accept that you're never going to know for sure...

... until you CLONE THEM!

*starts humming the Jurrasic Park theme song with a creepy grin on his face*

But having a 15 ft long neck which is held horizontal means you can browse a 30ft wide path without moving (or perhaps while moving slowly in one direction), the energy saving for being able to browse a large swath of ground without moving must be large when you weight a few tonnes.

Giraffe's have a rete mirabile [wikipedia.org] to avoid the head exploding when lowered. This sort of structure has evolved seperately in several unrelated species, so it's quite reasonable that the long-necked dinos had them. The dinos probably didn't need a large blood supply to the brain, the way a mammal does, so the requirements might not be so bad.

I'm sorry, but reading this completely unrelated tangent, the only thing I could think of was:

Oh yeah, the important thing was that I had an onion on my belt, which was the style at the time.They didn't have any white onions, because of the war. The only thing you can get was those big yellow ones...

But having a 15 ft long neck which is held horizontal means you can browse a 30ft wide path without moving (or perhaps while moving slowly in one direction), the energy saving for being able to browse a large swath of ground without moving must be large when you weight a few tonnes.

Ever held your arm out straight and put a large book on your palm & tried to keep from moving? The idea that solving for the blood pressure problem by having horizontal necks makes more sense than solving for the muscle fatigue problem by aligning the neck vertically is ludicrous.

Try standing perfectly still for hours on end, not flexing your legs even one bit. Sure, circulation will still happen (it's not like the circulatory system is one single loop, it's more like a beltway with various on/off ramps to do your thing in the city, then get back on the beltway in a totally different location), but blood will pool in your legs and it can cause issues by stretching out your veins and you'll start to feel light-headed and might even pass out.

As a results, veins are basically one-way valves. By flexing your muscles, you constrict your veins, forcing the blood within to go in the only direction they allow (back towards the heart).

Do they take account of the fact that the blood comes back down again? You might need a heart that size if you are pumping the blood at atmospheric pressure but if you keep the pressure built up on the veinous side, you just need to provide a pressure differential and to overcome viscous resistance.